1. Field of the Invention
The present invention relates to an image forming device that forms images on a recording medium, and more specifically to an image forming device that forms images by transferring a developed image from an image carrying member onto a recording medium via a transfer member to which a transfer bias is applied.
2. Related Art
An image forming device well known in the art includes a transfer member for transferring a developer image carried on an image carrying member to a recording medium, a bias applying member for applying a transfer bias to the transfer member, and conveying members for conveying the recording medium through between the image carrying member and the transfer member in coordination with the operations of the image carrying member. Through the effects of the transfer bias applied to the transfer member, the developer image carried on the image carrying member is transferred onto the recording medium.
The magnitude of the transfer bias in this type of image forming device can conceivably be adjusted according to various conditions. For example, when maintaining the transfer bias at a constant current, the areas of the image carrying member that directly contact the transfer member increase as the width of the sheet decreases, increasing the potential for current leakage. Therefore, consideration has been given for increasing the absolute value of the transfer bias current as the sheet width decreases, as disclosed in Japanese unexamined patent application publication No. HEI-10-301408, for example.
However, if the absolute value of the transfer bias current is increased too much, then the transfer bias can exceed a withstand current of the image carrying member, such as a photosensitive drum, and the like, inviting damage to the same. As a result, there is a possibility that a poor transfer will occur due to insufficient electric current or the like because the magnitude of the transfer bias cannot be increased to exceed a prescribed value.